The dibenzenesulfonimide of Formula I is a useful intermediate for the preparation of corresponding N-fluorosulfonimide of Formula II. The use of N-fluorosulfonimide for fluorination of nucleophilic organic compounds is well known. Further, these fluorine substituents play an important role in preparation of pharmaceutical and agrochemical agents.
where R1 and R2 are independently selected from group consisting of fluorine, chlorine, bromine, iodine, C1-6 alkyl, C1-6alkoxy, C1-6alkylsulfonyl, C1-6perfluoroalkylsulfonyl and cyano.
The process for the preparation of substituted and un-substituted benzenesulfonimides has been studied widely, for example, U.S. Pat. Nos. 2,891,979 and 5,254,732. Most recently the CN patent application 101671285 provides a process for preparation of dibenzenesulfonimide by reacting benzenesulfonamide with benzene sulfonyl chloride in the presence of sodium hydroxide and water.
The present inventors have observed that use of inorganic strong bases and water, such as alkali hydroxides and water, while condensation of benzenesulfonamide with benzene sulfonyl chloride results in great yield loss. This is primarily because benzene sulfonyl chloride gets hydrolysed to corresponding acid in the presence of inorganic strong bases and water, thus resulting in yield loss. Further, the inventors of the present invention found that the condensation of benzenesulfonamide with benzene sulfonyl chloride in the presence of compound of Formula V results in unexpected increase of reaction yield and simultaneously avoids any side reactions.